The invention relates to a device for actuating a control member, particularly a throttle valve in a gas conduit, such as for example an intake of an internal-combustion engine, which valve is pivotable from an idling position into operating positions by means of a valve shaft, the valve shaft carrying an actuator body comprising a magnetised rotor body which, via an air gap, cooperates with pole shoes of a stationary excitation section, which is electrically energisable by a regulator, which pole shoes surround said rotor body externally.
EP 0,375,050 B1 describes a device for actuating a control member, which can be controlled by an electrical regulator. The control member is, for example, a throttle valve of the engine of a motor vehicle, which valve is mounted on a valve shaft. The valve shaft carries an actuator body in the form of a magnetized rotor body having two poles. The permanent-magnetic rotor body is cylindrical and cooperates with an excitation section having three pole shoes which surround the rotor body so as to form an air gap. The pole shoes carry windings by which they are energized and which are each powered and controlled separately. In this way the throttle valve can be controlled in an accurately defined manner. When the windings are not energized a mechanical spring force ensures that the throttle valve is reset to a well-defined rest position. The construction and operation of the known device are also complicated, particularly owing to the fact that three currents have to be controlled and an additional mechanical reset mechanism.